GEOMAR Scientists Investigate Deep-Sea Mining Scars in the Clarion-Clipperton Zone

19 October 2026
Edited By: Haley McQueen

The research vessel SONNE has set sail from San Diego into the Pacific Ocean for expedition SO322. Its destination: the Clarion-Clipperton Zone (CCZ) north of the equator—the area that harbors the largest known deposits of polymetallic nodules on the seafloor. Germany, among others, holds an exploration license in this region.

Researchers can monitor what the underwater robot sees on the seabed while on board the vessel. The expedition includes researchers from 17 institutions across seven European countries. Their disciplines range from biology and microbiology to chemistry, oceanography and geology. (Image credit: Tim Kalvelage)

Under the guidance of Dr. Matthias Haeckel from the GEOMAR Helmholtz Centre for Ocean Research Kiel, a multidisciplinary team will investigate sites where nodule mining was tested five and a half years ago. The goal of the expedition is to assess the impacts on habitats in the water and on the seafloor. The results will directly feed into fact-based recommendations for international regulations of deep-sea mining.

Polymetallic nodules form at a snail’s pace. They grow about one to two millimeters over the course of a million years. If buried by sediment, they dissolve again. In their undisturbed state, they provide a habitat on the abyssal seafloor for animals that depend on a hard surface—which otherwise cannot be found there.

“Typically, we find two to three small organisms on each nodule,” said Matthias Haeckel. He is a biogeochemist at the GEOMAR Helmholtz Centre for Ocean Research Kiel and chief scientist of the SO322 expedition. Sea anemones, soft corals, or giant stalked sponges—which in turn provide a habitat for other organisms—are absent where the nodules have been removed. And because everything proceeds extremely slowly in the deep sea, Haeckel is certain: “Likely, we will not see any recovery.”

Five and a half years after the collector trials: How has life at the seabed changed?

In spring 2021, the Belgian company Global Sea Mineral Resources (GSR) tested a remotely controlled pre-prototype of a nodule collector system for 74 hours on the seafloor in the CCZ at a depth of more than 4,000 meters. During this time, the vehicle drove a distance of about 32 kilometers and harvested polymetallic nodules in an area of 54,000 square meters—an area roughly equivalent to seven soccer fields. The current expedition with RV SONNE will investigate effects at the seafloor five and a half years after this mining test. The expedition is part of the MiningImpact project, which has been studying the environmental impacts of potential future deep-sea mining since 2015.

collector system on the seabed. The SONNE expedition will now investigate the effects of this disturbance five and a half years later. (Image credit: ROV team, GEOMAR)

In addition to the removal of the biota-rich layer of surface sediments, another effect is the sediment plume that is suspended in the bottom water and resettles again within a distance of several hundred meters around the mining site. Fauna that are attached to the nodules (sessile fauna) cannot escape it and get buried.

Haeckel commented: “Some organisms can clean themselves, others cannot. Those that filter their food from the water are also very likely to be affected.” Investigating these effects is challenging, just as research in the deep sea in general is by no means easy. “We are still far from having a complete knowledge of the abyssal ecosystem; for example, we do not know what role the individual species play,” says the scientist shortly before his sixth research expedition to polymetallic nodule fields. “We’re only just beginning to understand the deep sea.”

Marine Technology from Benthic Landers to ROVs

To gain as much insight as possible during the expedition, RV SONNE carries a multitude of marine research gear: the remotely operated vehicle (ROV) KIEL 6000, which alone is the size of a small van and requires five 20-foot containers for cables, winches, the control unit, and accessories. The autonomous underwater vehicle (AUV) ABYSS with its launch and recovery system; three benthic landers that can be deployed at the seafloor; and sediment sampling devices such as multiple and box corers—a total of 16 containers of scientific equipment are on board. And the expedition time will be utilized to the fullest: RV SONNE will not enter any port for 54 days—the maximum stay at sea for which the ship is designed.

The ROV KIEL 6000 can dive to depths of up to 6,000 metres. It can collect samples from the seabed and take high-resolution photos and videos of the ocean depths. (Image credit: Tim Kalvelage)

In total, 39 researchers from 17 institutions and seven European countries are participating in the expedition—a multidisciplinary team drawing from the fields of biology, microbiology, chemistry, oceanography, and geology, each addressing a diverse range of research questions. In addition to investigating how faunal communities on the seafloor have changed five and a half years after the mining test and how long effects from the sediment plume persist, the scientists will also examine whether artificial hard substrates as a substitute for mined polymetallic nodules can promote recolonization of the seabed.

The Big Picture Is Still Unknown

Even if the above questions can be answered, the abyssal ecosystem remains largely understudied.

Haeckel explained: “Many species in the CCZ are extremely rare; about ninety percent of the species that we have sampled so far are still unidentified and have no name. And no one knows how many species are still to be discovered.” Another important topic about which little is known is species connectivity: “Many species are distributed across the entire CCZ between Mexico and Hawaii, in some cases even across the Pacific Ocean—which means gene exchange must be taking place. But we do not know what intermediate spatial steps and temporal scales are involved.” If this connectivity is to be disrupted by mining operations, the consequences for the deep-sea ecosystem will be immense.

The research vessel SONNE has set sail from San Diego into the Pacific. Its destination is the Clarion-Clipperton Zone near the equator, where the largest known seabed deposits of polymetallic nodules are located. (Image credit: Tim Kalvelage)

“This kind of large-scale damage must be prohibited, because we would only notice it if it is already too late,” added Haeckel. “The benthic ecosystem will not recover on human time scales. While the specific nodule habitat is removed permanently, sedimentary processes will be altered for thousands of years.”

Expedition at a Glance

Name: SO322 (MiningImpact project; NoduleMonitor3)

Chief Scientist / Project coordinator: Dr. Matthias Haeckel

Schedule: October 17, 2026–December 9, 2026

Start: San Diego

End: San Diego

Working Area: Pacific, Clarion-Clipperton Zone

About: MiningImpact

Since 2015, European scientists in the MiningImpact consortium have been assessing the environmental impacts of potential future deep-sea mining activities. The scientific findings are translated into recommendations for the International Seabed Authority (ISA) and national authorities. MiningImpact is funded under the Joint Programming Initiative Healthy and Productive Seas and Oceans (JPI Oceans) by the Belgian Federal Science Policy Office (Belgium), the Department of Work, Economy, Science, Innovation and Social Economy (Government of Flanders, Belgium), the Federal Ministry of Education and Research (Germany), the Ministry of Universities and Research (Italy), the Dutch Research Council (the Netherlands), the Research Council of Norway (Norway), Narodowe Centrum Badań i Rozwoju (Poland), and the Department for Environment, Food and Rural Affairs (United Kingdom).